Switched sockets?

[terry]

Am visiting the middle East and am told that wiring practices are 'per UK'. All house voltages nominal 230 volt at 50 hertz etc.

In my relatives 'villa' (two storey concrete block parged with cement and three big air conditioners on each floor!) the AC s are hard-wired to 230 volts. The AC outlets are the single socket variety which accept the 'usual UK' 13 amp fused plug.

Outlets are not as plentiful as in North American practice so the use of 'power bars' (often of dubious quality) is common. Some, ("From the republic", as locals will say) power bars, supposedly rated for say 15 amps seem to use the equivalent of AWG 18 wire! One, I looked at, didn't even have an earth conductor (deception?).

All/most outlets are switched with built-in small rocker type switch, each switch having a small neon indicator inside. As is normal in UK practice the switch is on when pressed 'down' (as opposed to North American 'up').

The sockets are mounted with ground/earth pin upwards (never sideways). Occasionally but not in this house one will see a double socket outlet plate but again each outlet has its own switch.

The dearth of outlets and some appliances which use non UK plugs (e.g. Schuko?) leads to the use of various adapters again often of dubious quality which I doubt would be approved for sale/use in the UK?

This is in comparison to our 37 year old home in Canada where our kitchen has six double/duplex 115 volt outlets on several radial circuits. Also the 230/115 volt electric cooking stove has its own 'individually wired' 50 amp socket; we have never used adaptors.

We understand the principle of the ring main although not used (AFIK) in our part of Canada. All domestic circuits seem to be radials. Wiring and fusing 15 amp for lighting, 20 amp for outlets, with limits on how many outlets on 'a run' and the use of either individual GFIs (Ground Fault Interrupters) i.e. RCDs, to protect outlets in outside/damp locations etc. With 30 amp for clothes dryers/water heaters etc.

Switches for lighting or incidentals such as bathroom fan but rarely for outlets (unless they are for table lamps etc.) in which case one may get one half of a duplex outlet switched (for lamps) and the other continuous (for radio, TV etc). that should not lose its power and thereby reset!

Question: Is/are switched outlets normal (UK) practice? If so why is each outlet switched? Curious.

PS: Unlike North American domestic practice which domestically are 3 wire 115-0-115 (i.e. 230 between two ends of the single phase) there are three phases coming into each individual residence in a compound of a couple of hundred. AFI can tell nothing here is connected phase- to-phase (that would be 400+ volts!). All loads are 230 volt and are balanced and distributed via the 3 phase circuit breaker panel (CU) .

[Dave Plowman (News)]

They normally are switched these days - and with a double pole switch.

When removing a plug with near maximum load on it you're likely to get quite a spark - and perhaps the same when inserting. The switch prevents this 'surprise'.

The design of UK sockets allows room for a switch - not so with many other country's types, so why not? They don't cost much extra and don't generally fail.

[John Rumm]

Probably more a comment on the age of the wiring I would have thought. I would expect newer builds have more plentiful outlets.

Common practice here would be for at least 10 double sockets in a kitchen these days.

It really should have an earth. Cable size for a 13A multi-way lead ought to be at least 1.5mm^2 per conductor. Note however if you are used to 115V leads, flexes used on UK style stuff may seem thinner than you expect since firstly it is running at half the current you are used to, and secondly each plug is fused. This allows the flex to have a lower current carrying capacity than the breaker that protects the whole circuit.

yup

Some makers here don't even bother making non switched outlets. Switched ones is very much the norm.

Well you can get adaptors for most types of plugs. They are rarely used here since everything sold will have the correct plug on it already. Hence you only usually need adaptors when travelling.

Common practice here would be to provide a dedicated ring circuit for all the general power sockets in the kitchen - starting with say 10 doubles for a smallish kitchen. Then to supply individual radial circuits for any specific high loads such as electric cookers etc, which may need a 30A or even 45A supply. Washing machines etc usually run from the normal power sockets. A common scenario is one power circuit per floor, with an addition one to the kitchen.

If you don't have individual overcurrent protection on each outlet, then high capacity circuits are harder to implement. Hence the "lots of radials" solutions in many countries.

We tend to use 6A for lighting circuits, and 32A on power circuits. A power circuit (ring) can have any number of outlets, but should be restricted to covering a floor space of no more than 100m^2. Typically a RCD will protect all general power sockets these days unless there is a specific reason for not doing so (i.e. dedicated feeds for freezers, heating systems etc, where a trip could have undesired consequences)

Common practice certainly. It provides an alternative way of switching something on or off. It allows the appliance to be isolated, but without the hassle of needing to unplug and reconnect each time (most switched sockets have double pole switching these days, although single pole is still available).

Power distribution here is also three phase (as it will be most places). Domestic premises are usually wired to just one phase. Phases are usually allocated in sequence to adjacent properties so as to spread the load among the phases. If you need more than a 100A supply then you may have three phase in a single property (and this would be common in multi occupancy blocks, and in industrial / commercial property). Its only usually industrial equipment that would require connection between phases.

[terry]

On May 3, 1:27 pm, John Rumm and Dave Plowman replied to terry ...................

Thanks John and Dave.

Very informative thank you for the discussion and so much information.

Double pole switches eh? Hmm! I must look at the ratings. My 230 volt North American table saw (less than one HP IIRC), needs a two pole switch!

Warm Regards. Terry.

[John Rumm]

You would probably be better of with a NVR switch for that (assuming it does not already have one). That way you can't get any nasty surprises should you trip a circuit and forget the saw is still switched on.

[Andy Wade]

Switched sockets do seem to be confined to the UK and countries using the BS 1363 (and BS 546 round-pin) systems. I suspect that the concept is a hang-over from the days of DC mains, and the long AC/DC era when accessories were marketed for use on either 'type of current'. (With DC a fast acting switch is needed to prevent sustained arcing. Unplugging, say, a 3 kW heater on DC would be pretty dangerous without the means to switch off first.)

For a while at least one manufacturer (Crabtree) had a proprietary interlocked system using a groove turned in the earth pin of the plug, such that you couldn't withdraw the plug unless the switch was off.

AFAIK BS 1363 accessories have always been AC-only, but by the time that standard appeared (1947) people had got used to switched sockets and the practice of including them just continued. They certainly add a degree of convenience missing in other countries' systems.

[Bob Eager]

As I discovered (to my parents' cost) when I was a small boy!

[Andy Hall]

What happened?

[Bob Eager]

Socket on skirting board near armchair. Folded newspaper beside chair. Large arc from withdrawn plug. Ignites newspaper and then chair.

I'm outside getting excited about the fire engine. Don't remember much more.

[Andrew Gabriel]

When I was a student, the labs in the UCL Physics department all had socket panels with 240V AC, 220V DC, and 12V. I was using the

220V DC to run a carbon arc lamp. If you pull out the plug without switching off, you just draw a long arc from the socket as the current doesn't stop flowing (well, it does when you drop the plug in surprise).

[Andrew Gabriel]

This is also what I've been told -- switches on sockets had simply become expected. There's no regulatory requirement for them now, and you can buy sockets without them, but they're rarely found.

[Brian Sharrock]

SNIP

Yup; I noticed that the local chippy [vendor of locally cooked potato 'french (freedom) fries] had prominent markings on some outlets 'WARNING - TWO PHASES'. which were feeding the fryers,

[Brian Sharrock]

The usual wiring to US power distribution is a single phase off a three phase supply to the house. (alternatehouse/blocks/ etc. receiving different phases for balance purposes This is a sinusoid of 220V AC. The phase (as we understand it ) is fed to the primary of a centre-tapped transformer from which two mutually antiphase components are drawn off. One 'wire' feeds some of the house; t'other feeds some of the house.

To power 'heavy' current drawing devices , such as table saws, US practise is to feed both antiphase waveforms to the device, - +110V(AC) and -110V(AC), giving them a 220V sinusoidal supply.

Americans refer to this as a 'two-phase' supply!

The OP's 'needs' a two pole switch because he's switching two separate supplies; unlike the UK wiring practise where a two-pole switch is interrupting the Live and Neutral conductors. When our site party was working in USA, we had difficulty in communicating with the natives; 'That's a two phase motor!' ... "Doesn't it run lumpy?" .... "Oh, You mean a 220V single phase!".

I suppose 'they' must have NVR switches too, but they're unlikely to be compatible with a UK design.

[Andrew Gabriel]

Your description is correct, except US has been 120V/240V for decades now, and they definately don't call this 'two-phase'. It's often referred to as an Edison supply, but is regarded as a single phase supply. A 'two-phase' supply in the US is a 4-wire circuit, with each pair carrying a supply which is

90º out of phase with the other pair. It's used for driving motors.

[djc]

Dosn't sound right to me. Both the round pin sockets in my grandparent's house (victorian, wired 1920s?) and the Bs1363 in my parents late 50's house did not have switches. Nor did the extra ones my father added over the next 20 years. Switched sockets became the norm sometime in the 70's or latter, much the same time as the upper part of the pins becaome sleeved. And probably for the same reason: if the plug is hard to pull out, the fingers curl around the top of a live plug.

[Steve Firth]

Hell, I must be imagining the switched sockets in my place in Italy then.

[Steve Firth]

Errm no.

We had switched 5A and 2A sockets back in 1964. And I think they were a lot older than that.

[tinnews]

Yes, that's my memory too. Certainly my parents' 1950s built house which had the 'new fangled' ring main had all unswitched 13 amp BS

1363 sockets.

[Dave Plowman (News)]

My parent's house was built in the '30s and all the sockets were switched. And it was AC from day one.